Robonova Screws?

[PaulL]

I've been trying to locate the PH/T-2 2 x 4 NI screws, but am not having any luck! These appear to be .91 mm pitch screws, but all I seem to find are the .4 mm pitch ones! The .91 mm pitch screws I've found are close, but not quite right (star head, triangular shank, etc).

Can someone point me to a source for these screws? I've tried mcmaster.com, and microfasteners.com, and several others... Maybe I'm not looking in the right place?

I'd really like to compile a list for all the RN screws and sources for them.

If I can be picky, I'd like to find .4 mm pitch and .91 mm pitch with socket heads in aluminum (anodized black), but I may be dreaming on that.

Thanks!
Paul

[serithseraki]

http://www.active-robots.com/products/r ... ries.shtml
The horn and screw set has eight of these. Good luck finding individual screws and if you do send me a link.

[PaulL]

Thanks for the link!

No such luck yet! Funny how these tiny screws are so hard to find!

[engineer]

micromark.com For $19.50 you get 1000 screws, try that item#83438, or you can order screws in the size you want, I get the longer ones at the screw shop in concord CA, but have to cut them down for the horns. The 5498SG's al horns don't come with screws and it's a pain. No matter what the prices are better than $1.00 for 4 screws at a hobby shop.

[PaulL]

Screw Update:

I found two of the main types of screws on http://www.mouser.com, and they seem to be identical so far. Ordered a bunch of each.

They Have:

Part Number 48SM004: M2 x .4 x 4mm, nickel plated, pan head philips.
This size is used for plastic-to-metal and metal-to-metal mounting in the RN-1. These should work for plastic servo horns (the bulk of the screws in the RN-1 kit), but not as well as the thread-forming ones that come w/ the RN-1. Those are almost impossible to find!!!

Part Number 481-0264: M2.6 x .45 x 4mm, nickel plated, pan head philips.
This size is used for the top plate mount, and for the bottom of the back cover mount.

Best of all, these are VERY CHEAP!!! USD $0.014 / each for 100+ for the M2's, USD $0.012 / each for 100+ for the M2.6's.

I ordered all I should ever need for less than $10.00 USD (not counting shipping).

I'll post back about them when I get them.

For black cap head screws, www.mcmaster.com has two options for these same thread sizes, though the M2.6 thread screws are only available in 8mm length. Check out 91290A011 and 91290A031.

Take Care,
Paul

Btw - Regarding the thread forming M2 screws on the RN-1, I found that I could order them from a custom screw shop, but the min order would be 1000 at a cost of around USD $500.00 or more. NOT COOL. I'll deal with the machine thread screws before I put out that kind of money for screws.

[PaulL]

Confirmed, the screws from Mouser fit (top plate, and bracket-to-bracket). You can use these in replacement of the screws that go in the plastic servo horns - this is what I intend to do with them. These are incredibly inexpensive screws compared to any others I have found!!!

[PaulL]

I ended up using these screws entirely in replacing all machine screws when I did a gold to silver bracket swap, and they look same as stock.

For some reason, the guy who built this bot I bought off ebay couldn't tell the difference between screws for plastic and machine screws, so I ditched all the machine screws that came in it, replacing them with the ones I mentioned on this thread.

And folks, if you're going to build an RN-1, use a thread locker on the metal-to-metal screws! If you don't, the joints will work loose, the alu brackets will rub, and the bot won't behave right.

And DON'T use plastic screws on the foot covers! Once you strip out the threads in the foot plate (and yes, you will!), it's a pain to get those screws back out, and even if you do, the hole is ruined.

Another builder's tip: make sure the bracket-to-bracket assemblies in the legs are square. I use the holes as a guide, and turn the bracket with a backlight (like a computer screen) to see that both holes on the sides of where the brackets meet "disappear" evenly. You would be surprised at how much you can throw off the dimensions of the 'bot if you don't square these up - might be enough to cause instability in motion, definitely can cause feet to not be parallel. Same goes for the servo in the foot, push it down, push it up, just don't let it sit crooked front-to-back or it will mess w/ the leg geometry a bit. Maybe this is a small detail, but why not make your 'bot the best 'bot it can be?

Take Care,
Paul